Boot sole



FIG. 1 is a bottom and right front perspective view of a boot sole showing my new design;

FIG. 2 is a right side elevational view thereof;

FIG. 3 is a bottom plan view thereof, the top being flat, plain, and unornamental;

FIG. 4 is a left side elevational view thereof. 

The ornamental design for a boot sole, as shown and described. 